Proximity sensing is implemented through two optical elements, one is a LED and the other is a light sensor. The light sensor captures the light signal coming from the LED to identify the presence, the position and/or the number of the object later in a controller. Specifically, the LED could be an infrared LED emitting infrared signals and the light sensor could be an infrared light sensor correspondingly. If an object is close enough, a part of the infrared light from the infrared LED reflects on the object and turns to enter the infrared light sensor. Then, the infrared sensor may generate signals corresponding to the sensed infrared light. After some signal processing sequence(s), such as signal conditioning, AC/DC converting or other sequence(s), the micro-processor or micro-controller may utilize the processed digital signals for identification. Now, proximity sensing plays a crucial role in industry of automatic machining, precision machining, semiconductor equipment and mobile devices.
Taking a mobile device with proximity sensing function for example, glass or other type of translucent material are utilized for covering and protecting a proximity sensing unit therein. However, this causes an undesirable consequence, the light sensor sensed a part of light emitted from the LED and reflected on the glass of other type of translucent material and incorrectly generates signals which may result in an incorrect determination of a close object. Moreover, the common tolerance for assembling the glass or other type of translucent material in the mobile device may effect the accuracy of the proximity sensing function.
For raising up the accuracy, the conventional solution is storing the value sensed by the proximity sensing unit therein to establish the basis for determination the presence of an object later on after the manufacturing process of a mobile device is done. For example, some parameters, such as threshold value and/or offset value, could be utilized for determination the presence of an object, and the aforesaid sensed value after manufacturing process could be taken as the offset value. When determining if an object is close, at least one threshold value could be utilized for comparing the resultant that the value sensed at the present moment minus the offset value with the threshold value.
However, actually, as the time runs and the environment outside the light sensor which may be influenced by a front cover sheet, paints, dirt changes, the decayed light sensor may be incorrectly determined an virtually non-existent object.
Therefore, a proximity sensing method to adapt to the changing of the environment or increase the accuracy is required.